fix bugs handling unicode file names

Fix crashes when handling non-ASCII characters in directory names and in
track titles.  In two places filenames were inadvertantly left as, or
converted to, a plain non-unicode byte string.  This caused decode
errors when we tried to concatenate them with Unicode strings, and
python attempted to automatically encode them as ASCII.

In album_dir.py, the input path was left as a plain byte string, rather
than being decoded as UTF-8.

In rename.py the safe_filename() function was inadvertantly converting
unicode input strings to plain byte strings in output, due to passing
the input through a non-unicode format string.

src/amass/archive/album_dir.py

@@ -8,6 +8,7 @@
 
 from .. import cdrom
 from .. import cddb
+from .. import file_util
 from .. import mb
 from .. import metadata
 from . import err
@@ -99,7 +100,7 @@ class DirLayout(object):
     layouts.
     """
     def __init__(self, path):
-        self.path = path
+        self.path = file_util.decode_path(path)
 
     def getMetadataDir(self):
         return os.path.join(self.path, 'metadata')

src/amass/archive/util.py

@@ -6,25 +6,12 @@
 import re
 
 from .. import cdrom
+from .. import file_util
 
 
 class FileInfo(object):
     def __init__(self, path, metadata):
-        # We generally encode the path names as UTF-8 when writing them.
-        # When reading path names, attempt to decode them from UTF-8 and
-        # convert them back to a unicode string.  This way we can compare them
-        # with the unicode strings that we use internally.
-        if isinstance(path, str):
-            try:
-                self.path = path.decode('utf-8')
-            except UnicodeDecodeError:
-                # Not a valid UTF-8 string.  Just keep using the plain
-                # byte array
-                self.path = path
-        else:
-            # Already a unicode string
-            self.path = path
-
+        self.path = file_util.decode_path(path)
         self.metadata = metadata
 
     @property

src/amass/file_util.py

@@ -53,3 +53,41 @@ def find_files_by_suffix(dir, suffix):
         files.append(path)
 
     return files
+
+
+def decode_path(path):
+    """
+    decode_path(str) --> unicode
+
+    Attempt to decode a byte string path name to a unicode string.
+
+    If the input is already a unicode string, it is returned as-is.
+    If the input is not valid UTF-8 and cannot be decoded, the byte string will
+    be returned as-is rather than throwing an error.
+    """
+    # We generally encode the path names as UTF-8 when writing them.
+    # When reading path names, attempt to decode them from UTF-8 and
+    # convert them back to a unicode string.  This way we can compare them
+    # with the unicode strings that we use internally.
+    if isinstance(path, str):
+        try:
+            return path.decode('utf-8')
+        except UnicodeDecodeError:
+            # Not a valid UTF-8 string.  Just keep using the plain
+            # byte array
+            return path
+    else:
+        # Already a unicode string
+        return path
+
+
+def safe_filename(name):
+    """
+    safe_filename(name) --> name
+
+    Make a string safe for use as a file name.
+    """
+    # TODO: It would be nice to strip out non-printable characters, or replace
+    # them with some dummy character.
+    # TODO: Support making the name safe for Windows, too.
+    return name.replace('/', '\\')

src/rename.py

@@ -9,18 +9,7 @@
 
 from amass import archive
 from amass import metadata
-
-
-def safe_filename(name):
-    """
-    safe_filename(name) --> name
-
-    Make a string safe for use as a file name.
-    """
-    # TODO: It would be nice to strip out non-printable characters, or replace
-    # them with some dummy character.
-    # TODO: Support making the name safe for Windows, too.
-    return name.replace('/', '\\')
+from amass import file_util
 
 
 def get_track_name(track):
@@ -30,7 +19,7 @@ def get_track_name(track):
     else:
         title = track.trackTitle
 
-    return safe_filename('%02d - %s' % (track.number, title))
+    return file_util.safe_filename(u'%02d - %s' % (track.number, title))
 
 
 def rename_files(info_list):